A glossary of mineralogy . occurs in me-talliferous veins with ores of silver, lead, andcopper, as well as with other ores of manga-nese, both massive and in botryoidal con-cretions lining cavities. Brit. Mus., Case 34. M. P. G. Principal Floor, Wall-case13 (British). DiAMANT. French for Diamond. DiAMANT dAlencon. See SmokyQuartz. Diamond. Cubical. Frequently in twincrystals, with faces often convex. Plane ofcomposition octahedral. Cleavage highlyperfect. Rarely massive. Lustre brilliant ada-mantine. Colour white or colourless, occa-sionally with tints of yellowy red, orange,green, brown, or b
A glossary of mineralogy . occurs in me-talliferous veins with ores of silver, lead, andcopper, as well as with other ores of manga-nese, both massive and in botryoidal con-cretions lining cavities. Brit. Mus., Case 34. M. P. G. Principal Floor, Wall-case13 (British). DiAMANT. French for Diamond. DiAMANT dAlencon. See SmokyQuartz. Diamond. Cubical. Frequently in twincrystals, with faces often convex. Plane ofcomposition octahedral. Cleavage highlyperfect. Rarely massive. Lustre brilliant ada-mantine. Colour white or colourless, occa-sionally with tints of yellowy red, orange,green, brown, or black. Transparent totranslucent when dark coloured. Fractureconchoidal. H. 10. 3-5295 to 3-55. Exhibits vitreous electricity when rubbed. Index of refraction 2-489, being often irre-gular, owing probably to the same causewhich has produced the convexity of itsforms. Becomes phosphorescent on exposure tothe light, and the smaller Diamonds becomephosphorescent by a much shorter exposurethan those of larger size. Fig. H5. Fig. 146. Fig. 147. Comp. Pure carbon crystallized. Burns no DIAMOND. at a temperature of 14° Wedgwood, and iswholly consumed, producing carbonic acidgas; also combustible in oxygen gas and inthe oxyhydrogen flame, and in the electricarc is converted into coke and graphite. The Diamond has in all ages been heldin the highest estimation. The most valuable are perfectly is rarely more than one tinge of colourin the same stone, but, Avhile it is consider-ably deteriorated by a dull or faint tint, itscommercial value, on the other hand, isgreatly enhanced by a well-defined tint ofpink, green, or blue. Diamonds are weighed in carats (151J ofwhich make one ounce troy) of o16 or 3^grains each. The medium value of a Dia-mond, when rough, is £2, and the value ofrough Diamonds of greater weight is esti-mated by multiplying the square of theirMeight in carats by 2, which gives the valuein pounds. Example:—To find, the valueof a rough Diamond 2 cara
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Keywords: ., bookcentury1800, bookdecade1860, booksubjectmineral, bookyear1861
